95 convertible idle issues stange power surges

Check and adjust your ignition timing sounds like one reasonable step you don't mention and doesn't require throwing more parts at the problem. Re-check the part in the surging idle checklist about setting your idle. In general, your car should idle (low) with the IAC completely disconnected. You accomplish this through adjustment of the throttle stop-screw and the idle air bleed.

The surging idle checklist is great of course, but it is a little more geared to the Fox setup. This thread contains a more effective procedure for setting the idle in the 94-95 in my opinion which includes using the idle bleed screw which I don't think the Foxes have. https://www.stangnet.com/mustang-forums/threads/where-is-the-iac-air-bleed-screw.609695/

What you're describing sounds like run of the mill surging with a little bit of hanging (revs up a bit when you press in the clutch), along with some bucking at cruise speed. If you don't have major vacuum leaks or other mechanical issues, you can coax away most of the surging with fine tuning the idle settings. Bucking at cruise speed might be helped by checking your timing, I've usually found it's either timing or a fuel problem (running a bit lean) so the only remaining part on your list I'd consider is the passenger o2 which might make a difference. I don't mind suggesting that because depending on how many miles you have, on a 20+ year old car, O2 sensors are really a maintenance item.

If it were my car, I'd check and adjust timing (spout out, 10 degrees btdc), change that passenger O2 if you don't know when (if ever) it's been changed, and then go through the thread I post for the idle adjustment procedure for the 94-95.